1. Technical Field
The present invention relates generally to the conversion of signals, and, specifically, to a delay line ramp demodulator formed entirely as an integrated circuit that demodulates a modulated signal and that may be employed with other signal conversion and processing circuitry.
2. Related Art
It is well known to modulate and demodulate signals in a signal transmission and receipt process. Typically, a signal of interest is modulated with a carrier signal at a transmit location to produce a modulated signal which is then transmitted or broadcast. The modulated signal may be transmitted via a wired link, a wireless link or a fiber optic link depending upon the particular application. One or more receiving locations receive the modulated signal, demodulate the modulated signal to reproduce the signal of interest and use the signal of interest. Typical applications include audio communication, video communication and data transmission. Commonly used modulation techniques include frequency modulation (FM), phase modulation and frequency shift keying (FSK).
Various demodulation techniques exist for demodulating a composite, intermediate frequency (IF) signal to extract the signal of interest. In a typical installation, dedicated demodulation circuitry employs a particular demodulation technique in demodulating each cycle of the IF signal. Because the IF signal is typically at a high frequency with respect to the signal of interest, the demodulation circuitry must operate within tight tolerances to accurately demodulate each cycle of the IF signal. These tight tolerances must be maintained through all operating temperatures so that the demodulation circuitry accurately reproduces the signal of interest. In prior art demodulation circuitry, high quality, low tolerance lumped elements were employed to precisely tune the demodulation circuitry and to guarantee that the demodulation circuitry would function accurately over all variations in operating temperature.
In prior art implementations, a portion of the demodulation circuitry was formed as an integrated circuit to reduce cost and to reduce power consumption. High quality, tight tolerance external elements were then connected to the integrated circuit via external connections as were required for tuning of the demodulation circuitry. The external elements were expensive and significantly increased the cost of the demodulation circuitry. Further, the external connections typically included lengthy electrical paths that consumed both board space and integrated circuit space. In addition, the external connections were prone to failure, increased power consumption and increased thermal output. Prior art demodulation circuitry typically operated only for specific IF signal frequency ranges. Thus, the demodulation circuitry was designed and built for particular applications and had little use other than in the particular application.
Thus, there lies a need for a demodulator that may be constructed as an integrated circuit that does not require external components. Further, there lies a need for such a device that may be adjusted for the demodulation of various carrier frequencies.